Not Applicable.
The present invention relates to mining. More specifically, the present invention relates to a self-inflating borehole plug for use in sealing an explosive column.
Typically, boreholes are dug and used as explosive columns. Detonation of a typical, full column confined charge produces a single high amplitude stress wave that crushes the borehole wall and moves out into the surrounding rock producing a crack mechanism. In conjunction with the stress wave, high temperature gases assist in extending the crack formation and moving the rock mass of the ground and sublayers.
By incorporating an air gap (air deck) above, below, or within the explosive column, shock wave reflections within the borehole produce a secondary stress wave. This wave extends the crack formation before gas pressurization. The reduced borehole pressure caused by the air column reduces excessive crushing of the rock adjacent to the borehole wall but still is capable of extending the crack formation and moving the rock out away from the opening of the hole. Air deck volumes of up to about 50% can be used before there is any reduction in fragmentation. By using an air deck, smaller amounts of explosives may be used without much change in fragmentation.
Self-inflating plugs, such as gas bags, are used to seal boreholes at various depths. One disadvantage with gas bags currently available is that they leak over time and thus have a limited shelf life. Another problem with bags currently available is that precise amounts of acid are not used, thus causing variations in performance. In some cases, vinegar is used as the acid, and the concentration of acid in the vinegar is not always consistent. Still another disadvantage with currently available gas bags is that they are folded such that the folds sometimes prevent them from fully inflating and expanding.
In order to overcome these disadvantages, an improved gas bag is provided. This gas bag is able to fully expand to tightly fit within a borehole. It may further be used to create air decks of various volumes.
It is an object of the present invention to provide a gas bag that is folded in a way that can easily inflate completely and seal the borehole.
It is another object of the present invention to provide an inflatable gas bag that is durable so that it has a longer shelf life than conventional bags.
It is a further object of the present invention to provide a method of making the inflatable gas bag of the present invention.
According to the present invention, the foregoing and other objects are achieved by a chemically inflated gas bag that includes a high density polyethylene (HDPE) bag that contains acetic acid, a polyvinyl alcohol (PVA) water soluble bag that contains sodium bicarbonate, and a nylon/polyethylene (PE) bag wherein the HDPE bag and the PVA bag are contained within the nylon/PE bag. Another aspect of the present invention is a method of making this gas bag. This method includes pouring diluted acetic acid into an HDPE bag and sealing said HDPE bag, putting sodium bicarbonate in a PVA bag, sealing the PVA bag, and placing the PVA bag and the HDPE bag within a nylon/PE bag. The gas bag is folded in such a manner as to easily inflate. Still another aspect of the present invention involves using this gas bag by lowering it into a borehole before or as it inflates.
Additional objects, advantages, and novel features of the invention will be set forth in the description that follows and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.